1. Field of Invention
The present invention relates to an active device array substrate and a display device. More particularly, the present invention relates to a thin film transistor array substrate and an E-ink display device.
2. Description of Related Art
E-ink display device was initially developed in 1970's. It is featured by a charged small ball with white color on one side and black color on the other side. The charged small ball rotates up and down to show different colors when the electrical field applied to small ball is changed. The second generation E-ink display device, developed in 1990's, is featured by a bi-stable charged particles which substitutes the conventional charged ball. The charged white particles may carry positive charge, negative charge or both. Nowadays, the major technical is using particles carrying positive/negative charge or using particles carrying single type charge/solution to display white/black colors.
In general, commercial E-ink display device comprises a front plane laminate (FPL) and a thin film transistor array substrate. Front plane laminate usually comprises a transparent cover, a transparent electrode layer and an E-ink material layer. The E-ink material layer comprises E-ink and supporting liquid. When the electrical field between each pixel electrode of the thin film transistor array substrate and the transparent cover of the front plane laminate is changed, E-ink will flow up or down to change optical property of each pixel.
After the thin film transistor array substrate and the FPL have been manufactured. It is always necessary to test the optical and electric property of wiring lines and pixels of the thin film transistor array substrate to ensure a good yield rate of E-ink display device. Before the driving circuit has been formed, a conventional shorting bar is used to test pixels. A gate shorting bar contacts to all scan lines and turn on all thin film transistors connected to all scan lines. A source shorting bar contacts to all data lines and a testing signal is input from the source shorting bar to data lines to input image data to every pixel so an image can be displayed and observed. The kind of test allows all thin film transistors and pixel electrodes to receive same signal. The existence of broken circuit leads thin film transistors and pixel electrodes to be unable to receive signal so an abnormal electric or optical behavior can be expected.
However, the above conventional test method is to input the same testing signal to all pixels so only the abnormal phenomenon of a specific displayed image can be observed, other pixel defects such as bright pint and dark point are not able to be observed. For example, two pixel electrodes of two neighboring pixels connected by residual indium tin oxide (ITO) is a type of defect which can not be detected by shorting bar because the testing signal for every pixel is the same no matter unanticipated residual ITO exists or not
Furthermore, other problems when using a shorting bar to test a device might be expected. A shorting bar is generally longer than the length of the area pressed by and contacted to the shorting bar to ensure all signal lines are able to receive signal. However, because of growing development of small-sized portable products, electric circuit is always restricted in a very small area. It is necessary to shorten the length of shorting bar so it can be fitted to small-sized portable products without possible short circuit problem caused by long shorting bar. But some signal lines might not be able to receive signal when using such short shorting bar to test devices. Furthermore, the effects of pressing and contacting signal lines are varied by material, shape of shorting bar and pressure applied to signal lines. Signal with different intensity might be transmitted to different) signal line due to the non-uniform pressure applied by shorting bar to signal lines. The accuracy of a test result is thus decreased if such problem exists.